Cooling blanket



Nov. 3, 1964 M. L. HIRSCHHORN COOLING BLANKET Filed Sept. 25, 1962 2Sheets-Sheet 1 INVENTOR TTORNE .Nov. 3, 1964 M. L. HIRSCHHORN 3,154,926

coounc BLANKET Filed Sept. 25, 1962 2 Sheets-Sheet 2 HOT JUNCTION j 30FIG. 7 Y///////////flifl COLD auucnou i INVENTOR V//////////////fl M2;L- mascnnorm L3, QwQHUILLWq ATTOR EYS United States Patent ""ce3,154,926 CDGLING BLANKET Max L. Hirschhorn, 56% 13th Ave, Brooklyn 19,N.Y. Filed Sept. 25, 1962, Ser. No. 226,092 4 Claims. (Cl. 62-3) Thepresent invention relates to a flexible cooling blanket device for thecontrol of animal body temperature.

It has been suggested that a refrigerated blanket be utilized to coolthe body in hot climates and in connection with surgical operations.Such blankets include devices which pump cooled air into the blanket andout through holes in one of its sides, blankets which are cooled byPeltier cells woven into the blanket, and blankets which are cooled byflexible plastic tubing wound within the blanket. These blankets haveprov-en to be either inefiicient in terms of heat transfer, cumbersomeor expensive.

In accordance with the present invention, a cooling blanket is providedin which cold fluid is pumped through a plurality or rigid metfl tubes.The ends of these rigid tubes are connected by flexible tubing and massof flexible metal wires or strips are connected between them. The metaltubes and the metal connecting wires or strips provide efllcient heattransfer from the pumped cooling liquid to the body and the blanket isflexible in one direction.

It is an objective of the present invention to provide a relativelyeconomic and eflicient (in terms of cooling power) cooling blanket.

Other objectives of the present invention will be apparent from thebelow detailed description taken in conjunction with the accompanyingdrawings, in which:

FIGURE 1 is a top plan diagrammatic view of an electric blanket of thepresent invention together with its associated refrigerating and controlsystems;

FIGURE 2 is an enlarged partial side plan view of the portion of thetubing of the blanket of FIGURE 1 without its insulation and attachedwires;

FIGURE 3 is a top plan sectional view of the tubing of FIGURE 2 coveredwith insulation and attached to a wire;

FIGURE 4 is an enlarged top plan view of the curved joints of theblanket of FIGURE 1;

FIGURES is a perspective partial view of another embodiment of thetubing of the blanket;

FIGURE 6 is a circuit diagram of an electrical circuit utilized with theblanket of FIGURE 1; and

FIG. 7 is a fragmentary sectional view of the blanket taken along a lineparallel with the tube showing the relation of the outer and innerlayers of the blanket to the coolant tube.

In FIGURE 1 a cooling blanket of the present in vention is connected toa source of cooling liquid. This source includes a plurality of Peltiercells 19, each of which has a cooling fin 1% attached to its hot end.

In the Peltier effect a direct current passes through a junction of twodissimilar conductors and heat is absorbed or generated at the junction,depending on the direction of the current. A number of combinations ofdissimilar conductors exhibit the Peltier eliect including two diiierentmetals, a semi-conductor with a metal, a p-type or n-type semi-conductorwith a metal, and a p-type semi-conductor with an n-type semi-conductor.Preferably the combination of conductors has large thermoelectric power,low thermal conductivity, high electrical conductivity, and thematerials should be inexpensive, readily formable and easy to solder andweld.

Power for the Peltier cells comes from an AC. source which leads intothe primary of the transformer 5b.

3,l5d,926 Fatented Nov. 3, 1964 The secondary of transformer 5b isconnected to a fullwave DC. rectifying bridge which supplies DC. currentto the Peltier cells, see FIG. 6.

The cold side of the Peltier cells 19, i.e., the end of the cell whichabsorbs heat is in direct physical contact with a non-flammable coolingfluid 2.2, such as a methylone glycol water solution or a sugarsolution, which is suspended within the bath 21. The bath 21 has an exitport 23 and an entry port 24 so that the fluid 22 may be circulated. Alow-pressure continuous operating pump 25 circulates the cooling liquidfrom the bottom of the bath Zl at port 23, pumps it into the tubes ofthe cooling blanket and returns the fluid back into the bath throughport 24.

The cooling blanket comprises a plurality of rigid tubes 11 of a thermalconductive metal, such as silver, pure copper or a copper alloy. Each oftubes 11 includes a central hollow elongated tube 10 running the lengthof the tube and a spiral groove 33 cut on the exterior face of tube Ill,see FIGS. 2 and 3. Each tube is preferably about one foot long. A largenumber of flexible heat conductive metal wires 12 are wound about thetubes within the helical groove 13 and from one tube to another toprovide an array of wires thermally interconnecting tubes ll. Theoutside of the tubes are encapsulated in a heat insulative materiallllb, such as an epoxy resin plastic, to retain the wires in the groovesand to thermally insulate the tubes. Encapsulation of the tubes enablesthe heat absorption function, i.e., cooling to be performed by the Wiresand not directly by the tubes themselves, so that the cooling effect isdistributed throughout the blanket and is not localized around thetubes. The tubes 11 are connected end-to-end as a continuous seriesconduit by flexible tubing 26, for example, of French woven nylon. Theflexible tubing 26 is used both in straight segments and in U-shapedcurves as shown in FIG. 1. Tubing Ed is preferably flexible enough to heslipped over the end portions of tubes 11 and the hollow portions 14 ofthe sleeve tubing will thereby establish communication with the hollowportions of tubes 111. A firm and permanent connection between theflexible joints 26 and the rigid metal tubes is preferably made withepoxy resin plastic or a suitable equivalent so that the tubing isliquid tight throughout the series coolant carrying conduit.

In the embodiment of tubing and conductive mai terial shown in FIGURE 5,the tubing 27 consists of a channel-shaped heat insulative member,preferably of molded nylon, having an open side. A. thin heat conductivemetal sheet 29' is fastened over this opening and forms an elongatedfluid carrying cavity 28 running the length of the channel-shapedmember. The metal sheet 29 may alternatively be cut into ribbons so asto run perpendicular to the length of the channel-shaped members toprovide additional structural flexibility in the blanket. The ends oftubes 27 are joined end-to-end by appropriate flexible tubing, notshown, into an array so that the tubes 27 are parallel similar to theparallel array of tubes 11 shown in FIG. 1. Metal sheet 29 is preferablya foil of pure copper about or" an inch thick. The lower face of sheet29, as seen in FlG. 5, is disposed toward the body to be cooled andserves a similar function in the blanket as the wires 12 of theembodiment of FIG. 1, i.e., to distribute the heat absorption functionrather than to depend on the concentration of heat absorption in theimmediate vicinity of tubes 27.

In both embodiments, a temperature control device 7 having a dial 7a isplaced adjacent to the bath 21 (FIG. 1). This device functions tocontrol the temperature at which the blanket is to be kept. The manuallysobbing wires or sheet.

operated dial 7a is operatively connected to a thermostat unit, of theusual bimetallic type such as used in refrigerating systems, housedWithin a thermally-conductive hermetically-sealed housing 8. The housing8 is positioned in the coolant 2-1 as seen in FIG. 1 whereby thethermos-tat is rendered responsive to the temperature variations of thecoolant. The desired temperature of operation of the thermostat isselected manually by dial 7:: which is calibrated in the usual manner.The contacts of the thermostat are connected by conductors i and 52 tothe A.C. source in series relation with the source 5 and the primary oftransformer 51; to function as an on-oil switch for the system. Thethermostat thus will render the cooling circuit inoperative wnen thetempcrature of the coolant is within the desired range and render thecooling circuit operative when the temperature of the coolant is withoutthe desired range.

Potentiometer 8a is adjustable to vary the resistance in the directcur-rent portion of the circuit to regulate, in effect, the rate ofcooling by the Peltier cells 1'9.

If desired, operation of pump can be automatically under control of thetemperature control device '7 with appropriate circuit connections asdescribed above whereby the circulation of the coolant is synchronizedwith the operation of the cooling cells.

It is to be understood that other equivalent temperature controls may beused with the invention in order to regulate the blanket temperature toprevent the temperature drops below or the temperature rises above thedesired level.

in using the invention as a blanket for cool ng the body temperature ofanimals and the like, the array of tubes 11 or 2-7 and theinterconnecting wires 12 or sheet 29 are covered with a quilt shown infragmentary section in FIG. 7 made up of an outer layer 30 of heatconducting or insulating material and an inner layer 31 of heatconducting material. The heat conducting material may be a thin sheet ofcotton, si lr, linen or the like and the heat insulating material may bewool. The inner heat conducting layer is placed on the animal and allowsthe maximum heat transfer from the animal to the heat ab The outer layeris preferably provided with heat insulation material to retard thetransfer of heat from the ambient which otherwise would reduce thecooling efliciency of the blanket.

The remainder of the equipment is enclosed in appropriate containersremote from the animal.

In operation, the cooling fluid is circulated through the tubes inserial circuit, Withdrawing heat from the animal by means of thedistributed heat conductive wires 12 or sheet 29 to the coolant fluid 22within the tubes. The fluid during its contact with the cold junction ofthe Peltier cell 19 is cooled by the action of the cell. The heat fromthe fluid is dissipated in the hot junction of the cell being carriedaway by natural convection or a forced blower such as a fan or the like.

The invention depends on the fact that metal, and particularly copperand silver, are excellent conductors of cold. The comparative thermalconductivity in Btu. for certain material is as follows: copper 0.759,silver 0.81, lead 0.067, nickel 0.18, and aluminum 0.43. The distributedmetal portions absorb the heat from the body. By distributing the heatconductive material over the entire surface of the animal the heatabsorption is substantially uniform.

The invention thus provides a means of adjusting the temperature of thebody or portions of the body. A flexible blanket having good coolingefiiciency is provided which is of especial benefit in operative uses inwhich it is desired to cool the body temperature to as much as 30 orbelow its normal temperature.

1 claim:

l. In a cooling device including:

a reservoir having entrance and exit ports for refrigerating fluid,

a system of fluid-tight tubing rigid portions connected in series, theseries connected at one of its ends to the entrance port and at itsother end to the exit port,

a pump having its rotor in the fluid to circulate the fluid through thetubing, and

refrigerating means adjacent the reservoir to cool the fluid,

the improvements comprising:'

a plurality of flexible tubing segments connecting the rigid tubingsegments, and

a plurality of thin, flexible, good thermally conductive metal membersattached to the rigid tubing,

said flexible tubing segments and said fluid-tight tubing rigid portionsbeing substantially covered with thermally insulative materialsufficiently to thermally in sulate said tubing, and said flexiblemembers being covered with said thermally insulative material at theconnections to the tubing, whereby the flexible metal members onlyabsorb heat from the ambient and transfer the absorbed heat to therefrigeration fluid through said tubing.

2. A cooling blanket comprising:

a liquid reservoir having entrance and exit ports,

a plurality of rigid copper tubes covered with a thermal insulationmaterial and connected together by short flexibl plastic tubingsegments,

an electric liquid pump whose rotor is immersed in the liquid tocirculate the liquid through the tubing,

a plurality of Peltier cells adjacent the reservoir having its cold endsin contact with the liquid,

a source of direct current electricity connected to the Peltier cells,and

a plurality of thin, flexible copper members attached to the rigid tubesthrough the insulative covering.

3. A cooling blanket comprising: 7

heat insulated means for conducting a fluid coolant,

a fluid coolant in said means,

heat conductive means and means thermally connecting the heat conductivemeans to the coolant,

said heat conductive means being generally distributed throughout aplane of the blanket.

4. An article of manufacture suitable for controlling the temperatureadjacent a living body and adapted to be placed in contact therewith,comprising a blanket having an inner supporting flexible material ofhigh thermal conductivity for contact with the living body and an outersupporting flexible insulated material, a series of rigid insulated flid conduits arranged in a substantially parallel array disposed betweensaid inner and outer material, flexibe tubing segments connecting theends of said conduits in serial serpentine arrangement, a plurality ofthin flexible thermally conductive metal members attached to said tubingthrough the insulation therc of, means connecting the respective ends ofsaid tubing to refrigeration means remote from said blanket, refrigerantin said conduits and means for circulating said rctrigerant through saidconduits.

References Cited in the file of this patent UNITED'STATES PATENTS1,896,953 Hassell Feb. 7, 1933 2,620,170 Brickman Dec. 2, 1952 2,705,877King Apr. 12, 1955 2,938,356 McMahon May 31, 1960

3. A COOLING BLANKET COMPRISING: HEAT INSULATED MEANS FOR CONDUCTING AFLUID COOLANT, A FLUID COOLANT IN SAID MEANS, HEAT CONDUCTIVE MEANS ANDMEANS THERMALLY CONNECTING THE HEAT CONDUCTIVE MEANS TO THE COOLANT,SAID HEAT CONDUCTIVE MEANS BEING GENERALLY DISTRIBUTED THROUGHOUT APLANE OF THE BLANKET.